This invention relates to substantially linear ethylene polymers. In one aspect, this invention relates to such polymers grafted with an olefinically unsaturated organic compound, e.g., maleic anhydride, while in another aspect, the invention relates to blends of this grafted polymer with one or more other olefin polymers, grafted or ungrafted. In yet another aspect, this invention relates to blends of this grafted polymer with non-olefin polymers, e.g., polyamides.
The graft modification of polyolefins, such as polyethylene and polypropylene, with various olefinically unsaturated monomers is well known in the art. Such a modification renders an essentially nonpolar polyolefin material compatible, at least to some limited extent, with a polar material. This, in turn, impacts on the adhesive properties of the polyolefin, e.g., its ability to be laminated to a solid. For example, U.S. Pat. No. 4,198,327 teaches a modified crystalline polyolefin composition having improved adhesion to polar solid materials. U.S.Pat. No. 4,397,916 and 5,055,526 also teach adhesive resin compositions of modified polyolefins and laminates made from such polyolefins. In a like manner, Japanese publications J04153205-A and J59027975-A describe modified polyolefin compositions, including modified crystalline polypropylene, which have adhesive properties either as film or as in a multilayer laminate. In some cases, the adhesive properties of these modified polyolefins are not entirely satisfactory and as such, additional improvements in the adhesive properties of these modified polyolefin compositions are disclosed by the use of oils, waxes, styrene-containing polymers and other elastomer polymers, such as those disclosed in U.S.Pat. No. 4,908,411.
As these references suggest, much of the existing art is primarily concerned with the modification of these polyolefins to develop compositions having specific adhesive properties or improvements in adhesive properties. However, graft modification can have a detrimental impact on one or more other properties of the polyolefin. For example, U.S. Pat. Nos. 4,134,927; 3,884,882 and 5,140,074 all report undesirable changes in the rheological properties due to cross-linking of the modified material. These changes ultimately impact the processibility of the material and thus, its utility in commercial applications.